Human mucosal-associated invariant T (MAIT) cells are a recently characterized T cell population that is abundant in blood and mucosal tissues including gingival tissue. Importantly, MAIT cells are a unique interface between the immune system and the microbiome due to their ability to recognize bacterial metabolites presented by major histocompatibility complex-related protein 1 (MR1). Once activated, MAIT cells produce pro-inflammatory cytokines and cytotoxic effector molecules, which can lead to clearance of an infection as well as tissue destruction and pathology. Interestingly, inflammatory cytokines are sufficient to activate MAIT cells and induce effector function. This is beneficial in the context of an infection, but is also likely to contribute to immune pathologies. We propose to study how MAIT cell function is altered during peri- mucositis and per-implantitis. The latter is diagnosed when inflammatory factors result in destruction of the supporting bone and tissue ultimately leading to the loss of the dental implant. The overarching goal is to understand if MAIT cells contribute to the inflammatory environment in peri-mucositis and peri-implantitis and how their anti-bacterial properties are altered in these conditions. Defining the role of this novel T cell population, in highly relevant clinical scenarios, is significant because it allows us to understand the interplay of immune system and microbiome and needed to develop future therapeutic intervention strategies.